Lawn sweepers for sweeping material off of lawns, driveways, or other surfaces are known. The material may be grass clippings, leaves, branches, nuts, rocks, or other particles. There are various types of lawn sweepers including lawn sweepers that are towed behind a lawn tractor as well as lawn sweepers that are pushed by a user. Many of these prior lawn sweepers rely on rotation of a wheel of the lawn sweeper to drive the brush of the sweeper.
These wheel-driven units are not consistent in brush rotational speed due to the direct dependence of the brush speed on the wheel speed. When the lawn sweeper is moved slowly, the brush spins slowly; when the lawn sweeper moves faster, the brush spins faster. When thick grass or leaves are attempted to be swept up, a natural inclination of the user is to slow the ground speed of the tractor towing the lawn sweeper. Because the speed of the brush is proportional to the speed of the wheel, slowing down the ground speed of the lawn sweeper causes the brush to slow down which may cause the sweeper to become clogged. The operator therefore has to decide between speeding up for brush power or slowing down for precision and safety. It is counterintuitive to increase the ground speed of the lawn tractor as the lawn sweeper enters tall grass or wet leaves.
Another problem with wheel driven units is that a gear-up ratio is used to rotate the brush at a higher speed, but the gear-up ratio provides little torque to the brush when the lawn sweeper is being towed or pushed slowly. Because a smaller amount of torque is being applied to the brush, the brush propels the swept-up materials a shorter distance into a catch basket of the lawn sweeper. This front-loads swept-up materials into the basket and may cause uneven loading of the material within the basket.
Some prior lawn sweepers also have issues relating to changes in the height of the brush during operation of the lawn sweeper. For example, the brush height of these prior lawn sweepers may have to be adjusted when the lawn sweepers are connected to lawn tractors having different trailer hitch heights. Another problem with some prior lawn sweepers is that uneven terrain can cause the brush of the lawn sweeper to be too high off the lawn to sweep up material or can cause the brush to be too close to the lawn and dig into the lawn as the lawn sweeper is towed by the lawn tractor. Specifically, the lawn tractor towing the lawn tractor travels upwardly and downwardly over the uneven terrain before the lawn tractor does which causes the tongue of the lawn sweeper to raise and lower. The raising and lowering of the lawn sweeper tongue generally causes the sweeper head of the lawn sweeper to tilt about the wheels of the lawn sweeper which causes the brush to be too high off of the lawn or causes the brush to be too close to the lawn. Similar problems have been encountered with walk-behind lawn sweepers as a user pushes the lawn sweeper over hilly terrain. Because the user continues to hold the handle of the sweeper, the sweeper head of the lawn sweeper may tilt about the wheels and cause the brush to be too high off of the lawn to sweep up material or to be too close to the lawn and dig into the lawn.